Added to options page to let users change keyboard mappings.

chrome/browser/resources/chromeos/switch_access/keyboard_handler.js

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // TODO(elichtenberg): Move into custom logger class or somewhere else.
 let debuggingEnabled = true;
 
 /**
  * Class to handle keyboard input.
  *
  * @constructor
  * @param {SwitchAccessInterface} switchAccess
  */
 function KeyboardHandler(switchAccess) {
   /**
    * SwitchAccess reference.
    * @private {SwitchAccessInterface}
    */
   this.switchAccess_ = switchAccess;
 
+  /**
+   * User preferences.
+   *
+   * @private {SwitchAccessPrefs}
+   */
+  this.prefs_ = switchAccess.switchAccessPrefs;
+
   this.init_();
 }
 
 KeyboardHandler.prototype = {
   /**
    * Set up key listener.
    *
    * @private
    */
   init_: function() {
-    // Capture keycodes for keys 1 through 4, and 6 through 9.
-    let keyCodes = ['1', '2', '3', '4', '6', '7', '8', '9'].map(
-        key => key.charCodeAt(0));
+    this.updateSwitchAccessKeys();
+    document.addEventListener('keyup', this.handleKeyEvent_.bind(this));
+  },
+
+  /**
+   * Update the keyboard keys captured by Switch Access to those stored in
+   * prefs.
+   */
+  updateSwitchAccessKeys: function() {
+    let keyCodes = [];
+    for (let command of this.prefs_.getCommands())
+      keyCodes.push(this.keyCodeFor_(command));
     chrome.accessibilityPrivate.setSwitchAccessKeys(keyCodes);
-    document.addEventListener('keyup', this.handleKeyEvent_.bind(this));
+  },
+
+  /**
+   * Return the key code that |command| maps to.
+   *
+   * @param {string} command
+   * @return {number}
+   */
+  keyCodeFor_: function(command) {
+    return this.prefs_.getNumberPref(command);
   },
 
   /**
    * Handle a keyboard event by calling the appropriate SwitchAccess functions.
    *
    * @param {!Event} event
    * @private
    */
   handleKeyEvent_: function(event) {
-    switch (event.key) {
-      case '1':
-        console.log('1 = go to next element');
+    let key = event.key.toUpperCase();
+    switch (event.keyCode) {

[dmazzoni, 2017/06/15 22:37:39]

One possibility here would be a map from command name (like 'next') to
a command like this.switchAccess_.moveToNode(true). Something like:

commandMap['next'] = this.switchAccess_.moveToNode.bind(this, true);
...

Then you could iterate over the commands and if one of them
matches keyCode, call it (and log the command name).

[elichtenberg, 2017/06/20 01:02:30]

Done. Put command map in commands.js

+      case this.keyCodeFor_('next'):
+        console.log(key + ' = go to next element');
         this.switchAccess_.moveToNode(true);
         break;
-      case '2':
-        console.log('2 = go to previous element');
+      case this.keyCodeFor_('previous'):
+        console.log(key + ' = go to previous element');
         this.switchAccess_.moveToNode(false);
         break;
-      case '3':
-        console.log('3 = select element');
+      case this.keyCodeFor_('select'):
+        console.log(key + ' = select element');
         this.switchAccess_.selectCurrentNode();
         break;
-      case '4':
+      case this.keyCodeFor_('options'):
         this.switchAccess_.showOptionsPage();
         break;
     }
     if (debuggingEnabled) {
-      switch (event.key) {
-        case '6':
-          console.log('6 = go to next element (debug mode)');
+      switch (event.keyCode) {
+        case this.keyCodeFor_('debugNext'):
+          console.log(key + ' = go to next element (debug mode)');
           this.switchAccess_.debugMoveToNext();
           break;
-        case '7':
-          console.log('7 = go to previous element (debug mode)');
+        case this.keyCodeFor_('debugPrevious'):
+          console.log(key + ' = go to previous element (debug mode)');
           this.switchAccess_.debugMoveToPrevious();
           break;
-        case '8':
-          console.log('8 = go to child element (debug mode)');
+        case this.keyCodeFor_('debugChild'):
+          console.log(key + ' = go to child element (debug mode)');
           this.switchAccess_.debugMoveToFirstChild();
           break;
-        case '9':
-          console.log('9 = go to parent element (debug mode)');
+        case this.keyCodeFor_('debugParent'):
+          console.log(key + ' = go to parent element (debug mode)');
           this.switchAccess_.debugMoveToParent();
           break;
       }
     }
     this.switchAccess_.performedUserAction();
   }
 };